The present invention relates to a speed change device for bicycles, of the type comprising:
a front derailleur and a rear derailleur for controlling selective engagement of a bicycle chain respectively with a plurality of toothed crown wheels associated to the bicycle crank axle and a plurality of sprockets associated to the hub of the bicycle rear wheel,
a first and a second electric motor respectively associated to the front derailleur and the rear derailleur, for control thereof,
means for detecting the operative position of the front derailleur and the rear derailleur,
manually controlled activating means for activating the first and second electric motor, and
an electronic control unit for controlling the speed change device, which is connected to said first and second electric motor, said detecting means and said activating means.
A device of the above indicated type has formed the subject of Italian patent application No. T093A000503 filed by the same applicant on Jul. 8, 1993 and laid open to public inspection on Jan. 8, 1995, as well as of corresponding French patent application Ser. No. 2,708,559, and corresponding German patent application No. 44 22 845. An improvement of this device has also formed the subject of Italian patent application No. T094A000116 of Feb. 24, 1994, filed by the same applicant and still secret at the priority date of this application.